Soils are an extremely complex and important natural resource. For landowners, understanding the soil on your property is essential for making land management decisions and for optimising production. Healthy soils are essential for having a well–functioning landscape, optimal plant and livestock production, maintaining biodiversity and for security of our food systems.

There is so much information available. The goal here is not to replicate information that already exists (thus adding to the online information overload that already exists) but to link you to the right evidence-based sites and resources.

Resources at the bottom of the page have been selected for this page from the  RegenWA Resource Library.

This page has been specifically created with funding support from SoilWise and Lotterywest.

Soil Wise is funded by the National Landcare Program Smart Farms Small Grants – an Australian Government initiative. It is supported by Healthy Estuaries WA – a State Government program.

Soil pH

Soil pH is a measure of the acidity or alkalinity of the soil water and is a function of the concentration of hydrogen ions in the soil solution. Soil pH is expressed as a logarithmic scale from 1 to 14 with one being highly acidic, 7 being neutral and 14 being highly alkaline.

Optimal plant growth occurs between a pH of 6 to 8 (approximately neutral). Outside of this range, soils which are acidic or alkaline can restrict plant growth by influencing the availability of plant nutrients in the soil.

Measuring soil pH in the field:

Two methods are available to measure soil pH in the field:

  1. By using a simple pH kit with a universal pH indicator solution. When the universal pH indicator is mixed with soil a powder is added to this solution and the solution will change colour. The colour of the soil solution is then compared to a pH indicator colour chart which is used to interpret the pH value of the soil.
  2. Using a field pH meter, the measurement is taken on a soil solution consisting of one part soil to five parts distilled water (1:5).

Soil pH should be measured in the first 10cm (topsoil) and again at approximately 20cm (subsoil) as pH can change with depth.

Click here for or a step by step video guide on measuring pH.

Interpreting soil pH results

Table 8. Soil pH guidelines (Source: ChemCentre, 2016)

pH (H2O)

pH (CaCl2)




Extremely acidic



Strongly acidic



Moderately acidic



Slightly acidic



Near neutral



Slightly alkaline



Moderately alkaline



Strongly alkaline



Very strongly alkaline

Implications of soil pH

Soil pH can result in soil nutrients normally available to plants to be ‘tied up’ resulting in them becoming unavailable for plant growth. Soil pH can also result in the release of some elements, causing them to become toxic to plants.

For example, at:

Low soil pH – beneficial elements including molybdenum, magnesium, calcium and phosphorus can become less available to plants.

High soil pH – calcium can tie-up phosphorus resulting in reduced availability for plant growth

Signs and symptoms of acidic soils

Soil acidity is a much more common problem in Western Australian soils than soil alkalinity, and so in this guide, we will only cover soil acidity. Acidic soils (low pH) can have negative affects on plant root growth in two ways. Firstly, it can alter the nutrient solubility and accessibility, and secondly, it can impact biological activity.

Soil acidity can lead to some soil nutrients becoming more soluble in soils and can reach toxic levels, while other nutrients become insoluble and are no longer available to be used by plants for growth. Some of the signs and symptoms of altered nutrient solubility and availability include:

Increased Aluminium:

  • Root growth becomes stunted leading to reduced ability of plants to access soil moisture and nutrients.
  • Legume species may show reduced nodulation

Increased Manganese:

  • Can lead to reduced plant growth where pH is less than 5.5 (*only in some soils and only at particular times of the year). This is more of a problem in Eastern States soils.

Soil acidity can also negatively impact the functioning of soil microbes in soils. The presence of acidic soils can reduce the growth and reproduction of soil microbes such as bacteria and fungi. This leads to reduced microbial processes such as organic matter breakdown and nutrient cycling where soil acidity is present.

Another important component of soil biological activity which can be reduced in acidic soils is the nodulation of legumes. Legumes form symbiotic relationships with bacteria in the soil which allows them to fix atmospheric nitrogen, making it available in the soil for plant growth. Acidic soils have a detrimental effect on this process, as the root growth of legume plants and the survival of rhizobia bacteria are both reduced. This reduces the amount of nodulation of legume species, which in turn reduces nitrogen fixation and can lead to nitrogen deficiency.

Potential management options for acidic soils.

The application of lime is the most effective way of treating soil acidity. We recommend undertaking laboratory soil samples to get detailed information of the pH of your soil to make informed decisions on managing soil constraints including soil acidity.

Soil salinity is a measure of the soluble salts in the soil water. Sodium chloride is the most common soluble salt in soils and groundwater; however, a salt can be any molecule made up of cations (sodium, calcium, potassium) and anions (chloride, sulfate), therefore having no net charge.

Grey or white patches on the soil surface and the presence of salt-tolerant species (i.e., saltbush or samphire) are simple indicators that saline soils may be present in that location.

A pocket electrical conductivity meter (EC meter) can be used to measure the salinity of the soil profile.

Method for measuring electrical conductivity of the soil:

  1. Take one part soil (50g) and mix with five parts distilled water (250mL) in a container and shake so the soil and water solution are well mixed.
  2. Dip the EC meter probe into the solution and record the value as EC 1:5 mS/m. (Note: take note of the units on the meter in case conversions need to be completed to have a value in mS/m).


The soil texture group can influence soil salinity because of the degree of leaching of saline water through different soils. Different seasons can also influence the degree of salinity in a soil profile as winter rains can result in leaching. The degree of salinity for different soil textures is shown below:

Table 7. The degree of soil salinity (mS/m) from nil to extreme for sand, loam and clay soils. (Source: DPIRD, 2020).

Texture group

Soil salinity (mS/m)

























Dryland salinity and potential management options

Dryland salinity is a major soil constraint across Western Australia, with over 1 million hectares of land once suitable for agricultural production now affected. Dryland salinity is not something which can be completely reversed, however, there are several options available to manage it which can improve whole-farm productivity, reduce further degradation and protect our landscapes.

Benefits to managing salinity include:

  • Utilising land which is not suitable for crop or pasture production
  • Increasing profit by implementing alternative products which are tolerant to saline land
  • Provision of alternative grazing options for livestock
  • Decreased water and wind erosion.

Saline land management options:


Engineering strategies can be implemented on salt affected land and are designed to lower the water table which helps to lower the salt down into the soil profile. Engineering options can be divided into surface water management and subsurface water management.

Surface water management information can be found at DPIRD here.

Subsurface water management information can be found at DPIRD here.

Vegetation options:

Implementing salt tolerant plant species can be an effective management strategy for land which can no longer sustain crop production due to salinity.

Saltbush is a good option for saline areas as it can used to provide sheep feed and can in some cases help to lower the water table. It also benefits the land by reducing water and wind erosion and provides habitat for native fauna. More information here – Saltbushes for dryland salinity management in Western Australia | Agriculture and Food

Pasture legumes and grasses which have some salt tolerance are another option for utilising land which is mildly salt affected. DPIRD has some great information and details of suitable species which you can access here – Pasture legumes and grasses for saline land in Western Australia | Agriculture and Food

Revegetation of saline land is the final option for utilising vegetation on saline land. There are a range of species which exhibit varying degrees of salt tolerance which can be used for revegetation. Information on species suitable for Saltland revegetation can be found here –  Salinity tolerance of plants for agriculture and revegetation in Western Australia | Agriculture and Food

Soil biology  

Soil biology is another soil property that largely influences soil health and plant production. Soils are a diverse ecosystem of organisms forming a soil food web. The organisms which exist in soil range from microscopic bacteria, fungi, algae, protozoa and nematodes to easily visible earthworms, dung beetles, insects and small vertebrates.

Each of these organisms plays an essential and specialised role in the soil ecosystem and they rely on plants to obtain their energy. In consuming plant material, these soil organisms play a vital role in nutrient cycling in the soil, making essential nutrients available for uptake by plants and other living organisms in the soil food web. Exudates from some bacteria and fungal hyphae contribute to improving soil aggregate stability and soil structure by binding soil particles together. Microbes such as bacteria and fungi are also primarily responsible for breaking down carbon in the soil – these microbes can release enzymes that break down dead plant material and other organisms into smaller carbon compounds.

The amount of soil biology present in a soil is influenced by the soil types, porosity, vegetation cover and the soil management practices implemented.

Management options for improving soil biology:

  • Maintaining year-round groundcover
  • Planting diverse crop and pasture species
  • Reduced or no soil tillage
  • Reducing chemical use
  • Applying balanced fertiliser nutrition informed by soil sampling analysis results.
  • Grazing management – allowing pasture recovery

Organic matter

Organic matter is the component of soil made up of carbon-containing compounds which came from once-living organisms including plant material, animal remains, plant roots, cells, and tissues. The amount of organic matter in a soil is dynamic, an ever-changing balance between inputs and losses of organic matter through decomposition by soil organisms.

Soil organisms decompose organic matter, resulting in the release of nutrients such as nitrate, sulphate and phosphate which then become available for plant uptake and growth. Humus is the product of organic matter decomposition. Humus can store plant nutrients, improve soil structure, and hold soil moisture. The overall benefits of organic matter in soils are improvements to soil structure, improved drainage due to increased porosity, increased soil moisture, storage, and provision of nutrients for plant growth and an improvement in the cation exchange capacity.

Potential management options for increasing organic matter:

  • Growing perennial and diverse pastures
  • Growing green manure crops
  • Reducing cultivation
  • Utilising organic fertilisers

Assessing soil biology:

Cotton Strip Assay method

  1. Choose several sites across your property to test to provide you with some comparisons (include areas of your best, worst and average soils)
  2. At each of your sites, using a flat spade, create a vertical slit in the soil to a depth of 10-15cm.
  3. Insert a cotton strip into the vertical slit in the soil, leaving out approx. 5 cm above the soil so you can find it again!
  4. Push in the soil around the cotton strip so there is soil contact with the cotton strip on both sides.
  5. Mark your site or ensure you detail the location.
  6. Wait for 3-6 weeks before carefully digging up your cotton strip (dig the cotton strip out of the soil rather than pulling it out, as this will cause the cotton to tear).
  7. Gently remove as much soil as possible from the cotton strips.
  8. Once you have dug up all of your cotton strips from all sites, compare the amount of decomposition.

High degrees of cotton decomposition indicate the presence of an active soil biology.


Living and dead plant material form the components of soil groundcover. Establishing and maintaining groundcover can be a useful management practice for reducing water and wind erosion to conserve topsoil and can be an important factor for reducing evaporation of water from the soil.

Groundcover assessments are expressed as a percentage, with 100% groundcover meaning no soil can be seen and 0% groundcover equating to no groundcover present/completely bare soil.

Overgrazing, drought, cropping, tilling, spraying and machinery or animal traffic can all reduce groundcover. Maintaining groundcover at a minimum of 70% is optimal for reducing the impacts of wind and water erosion of topsoil on your property.

Method for assessing groundcover:

  1. Using a piece of wire or cardboard, make your own DIY quadrat 30x30cm.
  2. Note the date of assessment and location on your property so that you can repeat observations in the same location at different time intervals to assess changes.
  3. Choose a representative/uniform area (an area of growth that appears to be the average across the paddock – i.e. not an area of high or low growth or an area that receives more water or nutrients).
  4. Place the quadrat on the ground and estimate the percentage of groundcover present within the quadrat.
  5. Take photos to establish a record over time.

Note: It is important to consider what time of year you assess groundcover as it is highly variable across the year. Monitoring at least twice a year can be beneficial to assess the difference in groundcover % in different seasons.

Soil profile and soil horizons 

The soil profile is described as the total depth of the soil. Rock layers, water, hardpans and the lower limit of biological activity define the lower limit of the soil profile.

The depth of the soil profile can vary from shallow soil comprised of a few centimetres of soil over rock, to soil several meters in depth. The rooting depth of the soil is the depth to which plant roots can grow and so this part of the soil profile has the largest influence on plant production.

A soil profile can be divided into different layers or soil ‘horizons’. Different soil horizons have their own combination of soil properties that characterise them, including soil texture and colour. Each horizon can be defined by an upper and lower depth. The individual horizons combined form the soil profile.

The top surface soil layer is called the topsoil or the ‘A’ horizon. The topsoil usually has the highest amount of organic matter present of all the soil horizons which often results in this layer being darker in colour than the layers beneath it. This layer is very important for plant growth as it often contains much of the plant available nutrients.

Below the A horizon or topsoil is the B horizon. This layer generally has less organic matter than the topsoil and contains a higher proportion of clay. The depth and water holding capacity of this subsoil influences the plants’ ability to have full root growth. If a subsoil is compacted or has poor water holding capacity, root growth can become restricted.

The C horizon occurs below the B horizon and this layer is the parent material which the above soils form from. If this layer is shallow, plant root growth is restricted by the parent rock material.

Assessing the soil profile:

To assess the soil profile, dig a hole in the soil between 80 to 150cm deep. This is the minimum depth required to effectively analyse the soil profile for agricultural purposes. Measure the depth of the different horizons in the soil profile. Soil colour and texture changes will help you determine where one horizon ends, and the next one begins. Also assess the depth to which root growth occurs in the soil profile. It is also important to note that soil profiles can change across landscapes and so you may need to assess the soil profile across several different locations on your property to identify constraints impacting different areas.

When completing your soil profile analysis, see if any plant roots are present and to what depth – this can inform you if there is a soil barrier preventing plant root growth after a certain depth and you can use this information to help guide what soil management practices you may implement on your property.

Check out this link for a video on how to assess your soil profile.


Soil colour

Soil colour can be a useful indicator to predict several soil properties such as aeration, drainage, and presence of organic matter. It is also a helpful property in determining the soil horizons as described in the section above.

Soil colour is determined by four main factors. These include soil mineral matter, organic matter, the presence of iron and the soil moisture content. When assessing soil colour, it is best to do so on moist soil as the soil can appear lighter when dry.

Soil colour can be determined by assessing soil against a Munsell Soil colour chart. This is an international system which divides soil colour into the hue (the wavelength of the colour), the value (the tone – from light to dark) and the chroma (how saturated the colour is).

A Munsell colour chart is often used to assess soil colour more accurately, however, you can describe soil more simply without this chart by determining if it’s one of the five main colours: red, brown, yellow, grey or black. Other descriptions of soil colour include pale yellow, red-brown, yellow-brown, white, grey-brown and dark grey.

Some indications of soil properties that can be concluded from soil colour include humus being associated with black soils, red soil is associated with iron-oxides and white soils are associated with the presence of silicates or salts.

Some soils may have mottles present which are patches of colour in the profile different to the main colour dominating that soil layer.

Mottles may indicate several characteristics of the soil, such as waterlogging. For simple soil colour assessments, note the colour of the main mottles present and note which soil horizons they are present in throughout the soil profile.

This DPIRD document – “Soil groups of Western Australia: a simple guide to the main soils of Western Australia” – can be used to determine the soil group/s on your property and has a variety of information to guide you through the process. 


Soil texture

Soil texture is the proportion of sand, silt, and clay particles that make up the mineral fraction of the soil that heavily influences the physical and chemical behaviour of the soil.  Sand is a granular material composed of finely divided mineral particles. Silt is a granular particle between sand and clay particle size. Clay is a fine-grained particle; smaller than sand and silt.

Soil texture can influence soil ‘workability’, meaning the amount of water and air in the soil, as well as water infiltration. For example, sandy soil has low nutrient levels and poor water-holding capacity but is highly aerated. Clay soils have higher nutrients and higher water holding capacity but have less air-filled pores. Texture is not a soil property which can be altered but it is useful to understand your soil texture to guide soil management practices.

Soil texture estimation method:

Note – It is useful to determine the texture for each of the different horizons in your soil profile.

  1. Sieve dry soil using a 2mm sieve to remove stones and gravel.
  2. Estimate the percentage of stones and gravel in the soil from step one.
  3. From the sieved soil, take a small handful of soil into the palm of your hand.
  4. Add water to the handful of soil so it can be rolled into a ball and then knead the soil for 1-2 minutes. If you cannot form a bolus with the sample, then the soil is very sandy.
  5. Form a ribbon of soil by pressing the soil between your thumb and forefinger. The longer the ribbon indicates a higher proportion of clay.

Check out a video from Soil Science Australia here which shows you how to assess your soil texture.

Soil particle diameters:

  • Sand: 0.02 – 2mm
  • Silt: 0.002 – 0.02mm
  • Clay: less than 0.002mm

It is also important to measure the percentage of gravel in the soil as this influences the available water and nutrients. Gravel in soil occupies areas which would otherwise be occupied by sand, silt or clay particles and therefore has a number of implications for a range of soil properties. Gravel reduces the amount of water and nutrients in a soil. Gravel also has the effect of concentrating inputs such as fertiliser and herbicides. It is important to consider these effects when making soil management decisions, as several soil physical and chemical tests are only assessed using the sand, silt and clay components, omitting the effects of gravel.

Common field soil textures

Table 1. Field texture class descriptions as outlined by DPIRD (2020).

Texture group

Texture grade

Ribbon length (mm)

Description of soil






Very little coherence of soil particles and soil cannot be rolled into a bolus.

Loamy sand


Little coherence of soil particles with a very grainy feel.

Clayey sand


Some coherence of soil particles, grains of sand stick to hands and very little presence of organic matter.





Sandy loam

15 – 25

Soil can be rolled into a coherent bolus but can feel sand grains.




A soil bolus can be formed and is easy to manipulate. The soil can be rolled into a ribbon and is smooth with sand still present.

Sandy clay loam


Bolus can be strongly formed with a sandy feel.

Clay loam


Soil particles can form a smooth, strong bolus.





Sandy clay

50 – 75

A soil bolus can be easily formed and manipulated with sand grains present.

Light clay

50 – 75

A smooth bolus which can easily be worked, moulded, and rolled.

Medium clay


The bolus is smooth and can be moulded without cracking.

Heavy clay


A smooth bolus, easily manipulated and moulded and very resistant to cracking and shearing.


Properties of different soil texture grades. Source: Adapted from Donahue et al (1977) and SA Department of Primary Industries and Regions:


Texture grades



Sandy loams


Clay loams


Total available water

Very low to low

Low to medium

High to medium

Medium to high

Medium to low

Infiltration rate

Very high

High to medium


Medium to low


Nutrient supply capacity


Low to medium


Medium to high




High to moderate


Medium to low


Tendency to hard setting



High to moderate


Medium to low

Susceptibility to compaction



Moderate to high



Cation exchange capacity


Low to moderate


Moderate to High


pH buffering


Low to moderate


Moderate to High



Soil structure 

Soil structure is an important part of assessing your soil profile. Soil structure is how sand, silt and clay particles, as well as soil air pores are arranged. Soil organic matter acts to ‘bind’ these particles into aggregates. A good soil structure with lots of aggregates allows water, nutrients and air to move between the aggregates promoting good plant growth and strong microbial activity. Unlike soil texture, soil structure can be influenced by soil management practices.  

Soil particles may not bond at all and are known as ‘apedal soils’ (such as very sandy soils) and are essentially structureless. This can be due to a low proportion of clay or low presence of organic matter to bind soil particles into aggregates. These soils are associated with rapid drainage and poor water holding capacity.  

Soil aggregates are also known as peds and these can vary in size from 2mm – 500mm. Good soil structure is defined by peds which form a definite shape and are between 1mm and 60mm in size. Soils which are structured into aggregates are known as ‘pedal’. These soils have sufficient clay and organic matter to allow soil particle aggregation and have good water holding capacity and can effectively store water and nutrients, promoting plant growth. Soils with good structure allow good water infiltration throughout the soil profile whilst also allowing it to drain excess water through the profile.

Soil structure can be assessed via determining soil compaction, infiltration and the soil particle aggregation via assessing the degree of slaking and dispersion of a soil aggregate when it is immersed in water.


Soil compaction

Soil compaction can occur in the topsoil and subsoil. Many of the soils in WA are affected by or are susceptible to compaction. Soil compaction is where soil particles become densely arranged and poorly structured as a result of losing soil macropores (air pockets).  

Compaction can restrict plant root growth leading to reduced plant biomass and grain yield. Compaction can also reduce water infiltration throughout the soil profile. Compaction is commonly the result of heavy traffic wheel tracks and soil cultivation for cropping. Livestock can also cause compaction of the topsoil. 

It is also important to consider the time of year you are assessing soil compaction. Soils will be more compacted in summer months as soils are much drier and so measuring soil compaction during the growing season may give you a more accurate measurement. To have reliable comparisons between years, make sure you measure soil compaction at the same time of year.

Making an at-home soil penetrometer:

How to make your own soil penetrometer: Take 50 cm of 3mm fencing wire, using approximately 15 cm of the length to curve into a circle to form a handle. Mark the straight piece of wire forming the penetrometer at every 2 cm.

Measuring soil compaction:

  1. Push your penetrometer into the soil.
  2. Once you cannot push the penetrometer any further into the soil, remove it and note the depth to compaction.
  3. Repeat at numerous locations in the paddock to get an average depth of compaction.


Level of compaction and what this may indicate about your soil. (Source: North Central CMA, 2016 and DPIRD, 2020).

Depth of compaction

What does it mean?

Cannot penetrate the soil.

This indicates soils have surface compaction which could have occurred from machinery or stock movement. It may also suggest low levels of soil organic matter. Plant root growth is severely restricted.

Penetrates the soil less than 15cm

Indicates moderate compaction of topsoil. Plant root growth is restricted, and roots can grow horizontally rather than down through the soil profile.

Penetrometer can penetrate easily to 15cm or more.

Indicates no compaction of the topsoil and plant root growth is not restricted. Water can infiltrate the soil.


Soil water infiltration

Soil structure and compaction influence how water moves through soils and affects the rate of water infiltration through the soil.

Soil infiltration tests measure the rate of water movement into a soil. Soils which have a low infiltration rate are susceptible to runoff and water erosion and can have less water available to be used for plant growth. Soils with high infiltration rates can become waterlogged, resulting in the reduced presence of air-filled soil pores which can lead to restricted plant growth.

Method for measuring the rate of water infiltration:

You can make your own infiltrometer using a piece of PVC pipe 150mm in diameter and 110mm long.

  1. Remove any stubble or vegetation from your sampling area.
  2. Put the pipe 20mm into the soil ensuring it remains as level as possible.
  3. Press the soil around the edge of the pipe to prevent water leaking at the edges.
  4. Pour 500mm of water into the pipe, starting a timer from when all water has been poured in.
  5. Measure how much water has been absorbed by the soil in 6 minutes and then multiply by 10 to get the value in mm/hour.

Interpretation of results:

Table 9. Interpretation of water infiltration results (Source: NQ Dry Tropics, 2019)

Results (mm/hour)

Water infiltration score

0 to 25


25 to 100


100 to 250


More than 250

Very Good


Soil water repellence

Water repellence is a common problem in soils across Western Australia. Soils which exhibit water repellence are known as hydrophobic soils. Soils become water repellent when waxy organic matter accumulates at the surface of the topsoil. The waxy organic matter or hydrophobic compounds which lead to soils becoming repellent originate from microbial and plant sources.  

Soil texture largely influences development of water repellence, with sand textured soils being more susceptible to developing this constraint. This is due to sands having a smaller soil surface area which can become coated with hydrophobic compounds. Therefore, fewer hydrophobic compound coated sand grains are required for a sandy soil to become water repellent than a soil with a higher proportion of clay, which has finer particles and a much higher overall surface area. Clays therefore require more hydrophobic compounds for a sufficient proportion of particles to become coated causing it to become repellent.

The previous section looked at water infiltration of soils. As you have probably already guessed, water repellence has a large impact on infiltration rates of water into soils. Water repellence not only reduces overall water infiltration, but it also alters the path in which water infiltrates the soil. Instead of entering the soil evenly as it would in a non-repellent soil, water preferentially infiltrates old plant root channels and macropores and in sloping landscapes, the water will run off and pool in flat areas or depressions, eroding soils along the way. Uneven soil wetting and runoff can lead to uneven or delayed crop and pasture establishment and losses of crops and pastures can be significant.

Testing for water repellence:

  1. Using a water dropper, drop one drop of deionised water onto the surface of the soil from a height of approximately 1.5cm.
  2. If the drop forms a sphere on the surface of the soil, some degree of water repellence is present.
  3. Measure the length of time the drop of water remains on the soil surface – using the table below to determine the degree of water repellence:

Time (seconds)

Degree of Water Repellence

Less than 1

Not significant


Very low water repellence


Low water repellence


Moderate water repellence

More than 260

Moderate to severe water repellence


Soil aggregation

Slaking is when wetting of a soil aggregate occurs and the pressure of air becoming trapped in the soil pores causes the aggregate to break down into smaller particles. These smaller soil particles then block pores in the soil matrix resulting in the formation of a crust on the soil surface. This process occurs due to a lack of soil structure and physical bonds with organic matter and plant roots.

Dispersion is where moist or wet clay in a micro-aggregate of soil breaks up into individual clay particles, creating a milky appearance as seen below. These individual clay particles penetrate soil pores, sealing the soil surface.

For a step by step video on testing for slaking and dispersion, check out this video from Soil Science Australia


Testing for slaking and dispersion:

  1. Collect some soil samples from the soil horizons you are interested in, particularly the topsoil (0-10cm) and the subsoil.
  2. Using a shallow dish or glass jar, put a small amount of distilled water (about 30-40 mm depth or just deep enough to cover the soil aggregates) in the container,
  3. Place 3 completely air-dried soil aggregates 4-6mm in diameter (approximately pea-size) from your samples into the water.
  4. Slaking can be assessed after 5 minutes. Slaking can be scored from 0 to 4 as follows:



Table 2. Slaking score as determined by the degree of slaking of a soil (Source: NSW DPI, 2000).

Slaking Score



Soil aggregate remains intact = no slaking


The soil aggregate particles collapse at the edges of the aggregate, but mostly it remains intact.


The soil aggregate collapses into angular pieces


The soil aggregate collapses into micro-aggregates less than 2mm in diameter.


The soil aggregate breaks down into individual sand, silt and clay particles.


  1. Dispersion can be assessed at 10 minutes and 2 hours and is scored depending on the degree of severity as below:


Table 3: The degree of dispersion from 0 to 3. (Source: NSW DPI, 2000).

Degree of dispersion


0 (Nil)

No dispersion of soil particles seen.

1 (Slight)

Slight dispersion of the aggregate identified by a slight milky appearance surrounding the aggregate.

2 (Moderate)

Moderate dispersion with an obvious milky appearance.

3 (Severe)

Strong dispersion identified by a strong milky appearance with much of the aggregate dispersed outwards.


What do these results mean?


Table 4. The potential implications and possible management strategies for soil affected by slaking based on the degree of slaking present. (Source: NSW DPI, 2000).

Slaking Score

Implications and possible management strategies.

0 – 1

Soil remains stable when it becomes wet. 


The soil may form a loose surface crust.


The soil is likely to form a surface crust and management actions such as reducing cultivation, retaining stubble and applying gypsum may help reduce the impacts or to overcome this problem.


The soil is likely to form a crust and hard-set, particularly on sands and loams. Reduced cultivation, stubble retention and gypsum application can be used to manage these soils.



Table 5. The potential implications and possible management strategies for soil affected by dispersion based on the degree of dispersion present. (Source: NSW DPI, 2000).


Implications and possible management strategies.

0 (Nil)

Soil aggregates are stable.

1 (Slight)

Minor dispersion may occur, particularly after cultivation. 

2 (Moderate)

Soils may suffer from crusting and may have poor drainage in subsoils leading to water logging. Applying gypsum can help manage these soils.

3 (Severe)

Soil may have severe crusting at the surface and may become waterlogged due to poor drainage of subsoil resulting from clay particles infiltrating soil pores. Gypsum application can be used to manage these soils. Laboratory soil tests are useful here to inform on gypsum application rates,



A comprehensive list of podcasts relating to regenerative agriculture and other topics can be found in the ‘RegenAg101’ section. Here, we’ve listed specific episodes on soil health that we have found insightful. 

We would love to hear what episodes you think are worth featuring here. Email us at with your recommendations! 

Ground Cover – It all starts with the soil with Derek Smith: Mixed farmer from Guyra who has come a long way along the journey from conventional to regenerative farmer. Episode includes – importance of soil health, William Albrecht methodology, soil micobiology, links between soil health & human health, cation exhange capacity.

Soils for Life Podcast Episode 9 – You are what you eat, and the soil it grows in: Is soil the key to better human health? This podcast talks with farmers and two researchers about the question: ‘Is soil the key to better human health?’. Featuring Matthew Evans – Farmer, chef and food writer and the author of ‘Soil’, Courtney Young – Co-owner at Woodstock Flour and project manager at Soils for Life,  Robyn Alders – Honorary professor with the Development Policy Centre at the Australian National University, and Dr Stephan van Vliet – Assistant professor of nutrition at the Center for Human Nutrition Studies at Utah State University He holds a PhD in Kinesiology and Community Health. Dr. van Vliet also holds a Masters in Nutrition Science.

Ground Cover – From bare paddock to diverse landscape with Bruce Maynard: Improving Soil Health, No Kill Cropping, Self Herding and grazing management

More podcast series to spark your interest:

Books and e-books

We’ve compiled a list of soil-related books that dive deep into the science and importance of soil.

  • SoilsWest Soil Quality e-books
  • Growing a Revolution: Bringing Our Soil Back to Life – David R. Montgomery
  • The Hidden Half of Nature: The Microbial Roots of Life and Health – David R. Montgomery
  • Dirt: The Erosion of Civilizations – David R. Montgomery
  • Soil – Matthew Evans
  • Dirt to Soil – Gabe Brown
  • For the Love of Soil – Nicole Masters
  • The Soil Will Save Us – Kristin Ohlson
  • Cows Save the Planet: And Other Improbable Ways of Restoring Soil to Heal the Earth – Judith D. Schwartz
  • Groundbreaking – Phil Mulvey
  • The Wooleen Way – David Pollock

Coming soon…

This guide, which has been made to take out into the paddock with you, can help you visually assess the soil on your property. It outlines some of the most important soil properties to assess, including several physical, chemical and biological soil indicators. Simple methods for assessing these soil parameters have been provided in an easy to use step-by-step method. 

A visual soil assessment is a quick and simple method to assess soil condition. By assessing the soil parameters outlined in this guide, you will be able to identify factors constraining crop or plant production on your property. It may also help you identify if these constraints will have any influence on other soil parameters (i.e. the effect of soil pH on plant nutrient availability).  

By assessing and continually monitoring the soils on your property you can:

  • Identify what soil constraints are present;
  • Make informed property management decisions; and
  • Assess whether practices or management changes are improving or maintaining soil health.

This visual soil assessment guide is intended to be a short and easy to use, in-paddock guide for assessing soils. Links to additional and more in-depth information and support are provided throughout the guide. The methods provided are simple and can be done by landowners, however, if you are looking for more accurate results, we recommend undertaking soil sampling analyses completed by a laboratory.

This guide is relevant for landholders across Western Australia (WA) and the information provided is WA specific.

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